Fascene Airport: Take a taxi directly to Hell-Ville/Andoany: the airport is about 12 km away and the ride is roughly 15–20 minutes. Wikivoyage’s reported fare is about Ar15,000; treat that as a bargaining baseline rather than a current fixed tariff. There is no compelling tourist-transfer alternative.
Ankify port, mainland Madagascar: Use the shared speedboat to Hell-Ville. It takes about 40 minutes, costs roughly Ar20,000, and generally runs when full between 05:30 and 16:00. It is the practical mainland connection, but do not plan a tight same-day flight or onward bus around a boat that leaves only when it has enough passengers.